Potravinarstvo Slovak Journal of Food Sciences Potravinarstvo Slovak Journal of Food Sciences vol. 14, 2020, p. 254-257 https://doi.org/10.5219/1245 Received: 27 November 2019. Accepted: 12 April 2020. Available online: 28 May 2020 at www.potravinarstvo.com © 2020 Potravinarstvo Slovak Journal of Food Sciences, License: CC BY 3.0 ISSN 1337-0960 (online) 137Cs ACTIVITY CONCENTRATION IN MUSHROOMS FROM THE BOBRŮVKA RIVER VALLEY Petr Dvořák, Jana Doležalová, Katarína Beňová, Martin Tomko ABSTRACT A total of 505 mushrooms belonging to 9 species were collected in the 2017 and 2018 mushrooming seasons near Dolní Rožínka in the Bohemian-Moravian Highlands and analysed by gamma spectrometry for 137Cs activity. The greatest 137Cs activity of 575 Bq kg-1 was detected in the species Boletus edulis, which is just below the permitted limit in its native state. In contrast, the detected activity level was only 316 Bq kg-1 in the mushroom Imleria badia, which is reported to be associated with the highest cumulative capability of all fungi species. However, differences in mean contamination values were not significant (p <0.05) due to high variability. It was shown that activity concentration is not dependent on the weight (size) of Imleria badia. Our results also confirmed the generally well known lower 137Cs activity in Russula species belonging to the group of gill-bearing or lamella-bearing mushrooms. Keywords: radiocaesium; mushrooms; river valley; Boletus; Imleria INTRODUCTION badia (syn. Xerocomus badius) from the area called Staré The 137Cs isotope is one of more than 20 radioactive Ransko (the Bohemian-Moravian Highlands in the Czech isotopes of caesium. 137Cs isotopes are formed at relatively Republic). The results also show significantly lower levels high concentrations, reaching as much as 6.3 %, during the of 137Cs activity in Slovakia as compared to the Czech fission (nuclear chain) reaction in nuclear reactors Republic. (Söderlund et al., 2011). 137Cs activity depends not only on the contamination of Its negative biological effect is due to the emission of the environment, but also on the mushroom species beta particles with the subsequent conversion of 137Cs to (Kalač, 2001). The highest levels of radioactive caesium metastable 137Ba, which emits gamma photons of an contamination are found in saprophytic mushrooms (Duff energy of 661.7 keV (Wasek et al., 2014). and Ramsey, 2008). The mycelium of the non-edible Despite the fact that more time than the physical half-life mushroom Lactarius turpis (formerly L. necator) in of 137Cs (30.17 years) has elapsed since the Chernobyl Ukraine (1996 – 1998) showed an average activity of nuclear power plant accident (26 April 1986), there are 52.700 Bq kg-1 (Vinichuk and Johanson, 2003). still geographical areas with long-term persistent Most of the published papers are based on mushroom contamination (Smith and Beresford, 2005; Beňová et collection from a relatively large area (Chiaravalle et al., al., 2016). 2018). In such large areas there are a number of different There are species of mushrooms in coniferous forests factors that affect the final mushroom contamination with a great ability to accumulate radiocaesium. (Kalač, 2001; Dvořák et al., 2006). Mushrooms probably contribute to the long-term retention First and foremost, the deposition of 137Cs is unevenly of radiocaesium in organic layers of forest soils, especially distributed depending on the precipitation intensity, spruce stands (Steiner, Linkov and Yoshida, 2000). The latitude and altitude of the area (Lehto, Vaaramaa and radiocaesium activity concentration in mushrooms from Leskinen, 2013; Bulko et al., 2014). The contamination different areas of the Czech and Slovak Republics in of Europe by post-Chernobyl radiocaesium shows a 2000–2004 was reported by Dvořák et al. (2006). mosaic pattern with significant differences in relation to The highest 137Cs activity concentration, representing area activity (Nilsson, 2009). 6.263 Bq kg-1 of dry matter, was measured in Imleria Volume 14 254 2020 Potravinarstvo Slovak Journal of Food Sciences Scientific hypothesis weapons tests. Other factors that can affect the value of The aim of this work is to compare the 137Cs mushroom contamination in addition to the growth contamination of various mushrooms in a small relatively medium properties are the climate and the associated homogeneous conifer forest ecosystem in a river valley. amount of precipitation, as well as the sampling time and the fungus type itself (Heinrich, 1993). Furthermore, it MATERIAL AND METHODOLOGY has been found that the levels of radiocaesium in the Mushrooms were collected at a defined location in the underground parts of fungi (mycelium) are higher than the Bobrůvka River Valley (near Dolní Rožínka in the 137Cs levels in the aboveground parts such as the medulla Bohemian-Moravian Highlands) in the 2017 and 2018 and the cap (Vinichuk and Johanson, 2003). The mushrooming seasons. A total of 505 mushrooms of 9 distribution of radiocaesium in various above-ground parts different species, both common and rare in this particular of fungi is uneven, with higher activity found in fungi caps area, were collected (Table 1). (Heinrich, 1993; Mukhopadhyay et al., 2007). Native mushroom samples were homogenised. Activity Mushroom samples collected in coniferous forests are determination was carried out in the geometry of a 450ml characterised by a high content of radionuclides compared Marinelli vessel or a 200ml polyethylene vial. These two to mushroom samples collected in deciduous forests geometries corresponded to the quantities of mushrooms (Čipáková, 2004). 137Cs activity ranged between 273 and per sample. 1.165 Bq kg-1 in fresh mushrooms collected in the French Determination of 137Cs activity was performed by two Alps in 1999 – 2002 (Pourcelot et al., 2003). In contrast, gamma spectrometry systems using HPGe GC4018 (40% the highest contamination measured in the dry matter of efficiency) and HPGe GC2020 (20% efficiency) mushrooms originating in the Bohemian-Moravian germanium detectors, both with a resolution of 1.8 keV, Highlands (Czech Republic) was 2.263 Bq kg-1. verified by the Czech Metrology Institute. The Contamination levels in Slovakia were significantly lower measurement time was 18 hours. (Dvořák et al., 2006). The programs Genie 2000 (Canberra) and Gamwin Research conducted in Europe, Japan and North America (Nuwia Třebíč) were used for evaluation. The 137Cs in 2008 has shown that Boletus subtomentosus is the activity in all measured samples was higher than the species with the highest contamination levels of the entire minimum detectable activities (MDA). In addition to the Boletus family. The potential danger represented by this mass activity, the total combined standard uncertainty was mushroom is even bigger due to its presence in large calculated using the formula: numbers in all types of forests (Duff and Ramsey, 2008). 1 However, we could not find this mushroom species in the Bobrůvka River Valley. æ 2 2 2 2 2 2 2 2 2 ö2 u = çu + u + u + u + u + u + u + u + u ÷ The mushrooms analysed in our study were collected a è E p y s ss r t A M ø from a small area in pine tree habitats in areas of steeply where the individual standard uncertainties are as follows: sloping hillsides modelled by river erosion. The results for relative uncertainty for efficiency (uE), relative uncertainty 137Cs mass activities are shown in Table 1. The largest for peak area (up), relative uncertainty for yield (uy), 137Cs activity was found in the species Boletus edulis, relative uncertainty for time coincidence summing (us), amounting to 1.575 Bq kg-1 in native state, which is just relative uncertainty for electronic stability (uss), relative below the legal limit. However, this species also showed uncertainty for time (ut), relative uncertainty for decay the greatest variation range, as mushrooms with a mass (ur), relative uncertainty for self-absorption (uA), relative activity of 28 Bq kg-1 were also found. In contrast, the uncertainty for reproducibility (uM). greatest activity seen in Imleria badia, which as a representative of the Boletaceae family is often quoted in Statistical analysis connection with the highest cumulative ability, was only The weighted arithmetic mean, average total standard 316 Bq kg-1. The differences between the average uncertainty, and maximal and minimal value of mass contamination values of both mushroom species (197 and activity were calculated for statistical evaluation. A two- 173 Bq kg-1) were not, however, significant due to high sample unequal variances t-test was used to compare the variability. Kunová, Dvořák and Beňová (2006) reported mean differences. A correlation coefficient was calculated the highest 137Cs activity value measured in Imleria badia to compare the dependencies. from the Staré Ransko locality (the Bohemian-Moravian Highlands). This activity reached 708 Bq kg-1, which is RESULTS AND DISCUSSION around twice that of the mushrooms studied in our work. Mushrooms, as one of the most important components of Another representative of the Boletaceae family is the forest ecosystem, are able to accumulate a significant Xerocomellus chrysenteron. The variation range is from 19 amount of radionuclides, including 137Cs (Heinrich, 1992; to 2 Bq kg-1, which shows a very low ability to accumulate Škrkal et al., 2013; Guillen and Beaza, 2014). The first radiocaesium. Given the 33 specimens monitored, this mention of contamination of mushrooms with cannot be a coincidence. The results